1. Field of the Invention
The field of this invention is transdermal drug delivery, particularly, methods of producing topical patch preparations for transdermal drug delivery.
2. Background of the Invention
Transdermal delivery devices, e.g., topical patches, wound dressings, etc., are used to administer a variety of therapeutic agents, such as pharmaceutically active agents. The devices are generally applied to the surface of the skin and a therapeutically active agent contained therein is delivered to the systemic circulation via absorption through the skin. Advantages of transdermal delivery of a therapeutic agent over oral or parenteral administration include increased bioavailability (as first-pass liver metabolism is avoided), and more controlled (e.g., sustained, continuous) delivery. Topical preparations, e.g., topical patch preparations, for transdermal delivery typically contain an active agent dissolved or dispersed in an aqueous adhesive gel composition that is coated or spread onto a fibrous material.
Sterile topical patch preparations for transdermal delivery are currently commercially produced by clean room fabrication from sterilized components. The process requires specially designed facilities, special equipment, protective clothing for clean room personnel made of special materials (e.g., Tyvek(copyright)); and stringent environmental control and maintenance, e.g., of air quality, pressure, temperature and humidity. Accordingly, clean room fabrication is costly.
Accordingly, the development of methods of producing terminally sterilized topical patch preparations for transdermal delivery would be of great benefit in drug delivery.
3. Relevant Literature
Patents of interest include the following: 6,030,554; 6,028,242; 5,782,914; 5,730,933; 5,496,302; 5,011,660 and 4,652,763. See also U.S. Pat. Nos. 5,827,529; 5,480,649; 5,242,951; 5,116,621 and 5,082,663.
Methods of producing a terminally sterilized topical patch preparation are provided. In the subject methods, a topical patch preparation is exposed to electron beam radiation, preferably low level electron beam radiation, for a period of time sufficient to terminally sterilize the topical patch preparation. Also provided are the terminally sterilized topical patch preparations produced by the subject methods, as well as methods of using the same.
Methods of producing a terminally sterilized topical patch preparation are provided. In the subject methods, a topical patch preparation is exposed to electron beam radiation, preferably low level electron beam radiation, for a period of time sufficient to terminally sterilize the topical patch preparation. Also provided are the terminally sterilized topical patch preparations produced by the subject methods, as well as methods of using the same. In further disclosing the subject invention, methods for producing the subject topical patches and the patches themselves will be described first in greater detail, followed by a review of representative methods of using the topical patches.
Before the subject invention is described further, it is to be understood that the invention is not limited to the particular embodiments of the invention described below, as variations of the particular embodiments may be made and still fall within the scope of the appended claims. It is also to be understood that the terminology employed is for the purpose of describing particular embodiments, and is not intended to be limiting. Instead, the scope of the present invention will be established by the appended claims.
In this specification and the appended claims, singular references include the plural, unless the context clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood to one of ordinary skill in the art to which this invention belongs.
Method Of Producing A Terminally Sterilized Topical Patch Preparation
As summarized above, the subject invention provides methods for producing terminally sterilized topical patch preparations. The subject methods are suitable for use in terminally sterilizing a variety of different types of topical patch preparations. By topical patch preparation is meant a composition that includes an active ingredient in a topical delivery vehicle, i.e., a vehicle that is suitable for application to a skin surface (or epidermal surface) of an animal. A variety of different topical patch preparations are known to those of skill in the art. Representative topical patch preparations that may be terminally sterilizable according to the subject methods are provided infra. In many embodiments, the topical patch preparation is present in a sealed packaging means, i.e., it is sealed, as described in greater detail infra.
A feature of the subject methods is that the topical patch preparation, which in many embodiments is sealed in a packaging means, is exposed to electron beam irradiation for a period of time sufficient to terminally sterilize the composition while maintaining the activity of the active agent present therein. The topical patch preparation may be exposed to electron beam irradiation using any convenient protocol and device, where representative protocols and devices for exposing compositions of matter to electron beam irradiation are disclosed in U.S. Pat. Nos. 6,030,554; 6,028,242; 5,989,498 and 5,807,491; the disclosures of which are herein incorporated by reference. In many embodiments, the topical patch composition is exposed to low level electron beam irradiation. By low level electron beam irradiation is meant electron beam irradiation ranging in strength from about 5 to 19 kGy, and in many embodiments from about 8 to 15 kGy.
In practicing the subject methods, the topical patch preparation is exposed to electron beam irradiation for a period of time sufficient to terminally sterilize the topical patch preparation without adversely affecting the properties of the preparation to an unacceptable degree. Generally, the period of time during which the topical patch preparation is exposed to the electron beam irradiation is at least about 1 min., usually at least about 1-2 min. and more usually at least about 2 min., where the period of time may be as long as 3 min. or longer, but usually does not exceed about 5 min. and more usually does not exceed about 3 min. In many embodiments, the period of time ranges from about 1 to 3 and usually from about 1 to 2 min.
The above described process produces a terminally sterilized topical patch preparation. By xe2x80x9cterminally sterilizedxe2x80x9d is meant that the topical patch preparation is substantially, if not completely, free of viable microorganisms, where by xe2x80x9csubstantially freexe2x80x9d is meant that amount of viable microorganisms present in the patch preparation following the above described treatment does not exceed about 100, usually does not exceed about 10 and more usually does not exceed about 5 and by xe2x80x9ccompletely freexe2x80x9d is meant that no viable microorganisms are present in the topical patch preparation. As such, the subject patches are substantially, if not completely, free of microorganisms selected from the group consisting of: Staphylococcus aureus; Psedlomonas aeruginosa; Escherichia coli; Candida albicans; Aspergillus niger; and the like.
The subject methods are suitable for use in the sterilization of a wide variety of topical patch preparations. Examples of different types of topical patch preparations with which the subject sterilization methods may be employed include those described in U.S. Pat. Nos. 5,827,529; 5,480,646; 5,242,951; 5,116,621; and 5,082,663; the disclosures of which are herein incorporated by reference.
A representative topical patch preparation described in at least some of the above mentioned patents that may be terminally sterilized according to the subject methods is made up of active agent retaining layer present on a support, where the active agent retaining layer is made up of one or more active agents present in, e.g., dissolved in or dispersed in, and adhesive gel base, where the adhesive gel base is made up of a water-soluble high molecular weight substance, water and a water retaining agent.
Water-soluble high molecular weight substances include water-soluble polymers, where polymers of interest include, but are not limited to: gelatin, starch, agar, mannan, alginic acid, polyacrylic acid, polyacrylate, dextrin, methylcellulose, sodium methylcellulose, sodium carboxymethylcellulose, carboxyvinyl polymer, polyvinyl alcohol, polyvinylpyrrolidone, acacia, tragacanth, karaya gum, and starch acrylate copolymer. Metallic salts of these, as well as the products of cross-linking these by means of organic or inorganic cross-linking agents, are also of interest. These water-soluble polymers can be used to bring out the properties and characteristics of the other starting materials used in the adhesive gel composition, and in practice can be used alone or in combinations of 2 or more. The amount of water soluble high molecular weight substance(s) present in the adhesive gel base generally ranges from about 0.5 to 50, usually from a bout 5 to 25% by weight.
The amount of water present in the gel adhesive is sufficient to impart the desired physical properties to the gel adhesive, and generally ranges from about 10 to 70%, usually from about 20 to 50%.
The water-retaining agent or water-holding agent of the subject adhesive gel compositions is any agent that is capable of at least diminishing the volatilization of water contained in the adhesive gel base so that the water content in the adhesive gel base is maintained at least a substantially constant, if not constant, level during storage and use of the preparation. One or more water-retaining agents may be employed in the subject compositions, where the amount of water-retaining agent present in the adhesive gel base generally ranges from about 1 to 70%, more preferably 10 to 60% by weight. Examples of suitable water-retaining or water-holding agents include, but are not limited to: 1 or more types of polyvalent alcohols, such as glycerin, sorbitol, propylene glycol, 1,3-butylene glycol, and ethylene glycol, and the like.
Furthermore, in addition to the aforementioned ingredients, various additives that are used in ordinary topical water-soluble patch preparations may also be suitably compounded as needed, including inorganic substances such as kaolin, bentonite, and titanium dioxide; preservatives such as paraben; anionic, cationic, and nonionic surfactants; metallic aluminum crosslinking agents such as aluminum chloride, dried aluminum hydroxide gel, and dihydroxyaluminum aminoacetate; oils such as jojoba oil and castor oil; solubilizers such as crotamiton; chelating agents such as EDTA; pH regulators such as malic acid, tartaric acid, and diisopropanolamine; alcohols such as ethanol; moisture retaining agents such as hyaluronic acid, aloe extract, and urea; and other perfumes and coloring agents.
A diverse array of active agents or ingredients may be present in the adhesive gel base, described supra, in the subject topical patch preparations. Depending on the nature of the agent, the amount of active agent present in the composition generally ranges from about 0.2 to 10%, usually from about 0.2 to 5% and more usually from about 0.5 to 5%. Representative specific active agents of interest include, but are not limited to: dl-camphor, capsaicin, eucalyptus oil, nonivamide, methyl salicylate, glycol salicylate, dipotassium glycyrrhizinate, 1-menthol, and tocopheryl acetate; nonsteroidal antiinflammatories such as salts and derivatives of ketoprofen, flurbiprofen, felbinac, and diclofenac; and local anesthetics such as lidocaine, tetracaine, and xylocaine.
In many embodiments, the active agent present in the composition is a local anesthetic. Although two or more local anesthetic agents may be present in the subject compositions, generally the subject compositions will comprise a single local anesthetic agent. Local anesthetics of interest are those which, when administered in the topical formulations, rapidly penetrate a keratinized skin surface. In many embodiments, local anesthetics of interest have a molecular weight and melting point that is compatible with transport across the keratinized skin surface. Generally, the molecular weight of the local anesthetic will not exceed about 300 dal, and will more usually not exceed about 250 dal. The melting point of the local anesthetic will be less than about 100xc2x0 C. In many embodiments, the local anesthetic will be a compound comprised of a secondary or tertiary amine linked by a bond or through a connecting group to an aromatic group. The local anesthetic will generally be an alkanyl compound of from about 9 to 20 carbon atoms. Because the composition is applied topically, the local anesthetic will generally be present in the composition as a free base to promote penetration of the agent through the skin surface. A large number of local anesthetics are known in the art, many of which are suitable for topical application. Suitable local anesthetics include lidocaine, butamben, butanilicaine, ethyl aminobenzoate, fomocaine, hydroxyprocaine, isobutyl p-aminobenzoate, naepaine, octacaine, parethoxycaine, piridocaine, prilocaine, procaine, risocaine, tolycaine, trimecaine, tetracaine, xylocaine, ethylaminobenzoate (benzocaine); etc.
As mentioned above, the adhesive gel composition containing the one or more active ingredients is typically present on a support. The support is generally made of a flexible material which is capable of fitting in the movement of human body and includes, for example, various non-woven fabrics, woven fabrics, spandex, flannel, or a laminate of these materials with polyethylene film, polyethylene glycol terephthalate film, polyvinyl chloride film, ethylene-vinyl acetate copolymer film, polyurethane film, and the like.
In many embodiments, the to be sterilized topical preparation or patch is present in a sealed package prior to exposure to electron beam irradiation, as described above. Generally, the sealed package is fabricated from a packaging material that includes a layer made out of a material capable of preventing passage of moisture, oxygen and other agents, i.e., the package includes in a moisture/oxygen barrier material. Any suitable barrier material may be employed, where barrier materials of interest include metalic layers, e.g., aluminum, where in many embodiments, the barrier layer is an aluminum layer. This barrier layer has a thickness sufficient to provide for the barrier function, where the thickness typically ranges from about 5 to 15, usually from about 6 to 10 xcexcm. In many embodiments, the package is a laminate of the barrier layer in combination with one or more additional layers, e.g., polymeric layers, paper layers, etc. A representative aluminum containing package that may be used with the subject patch preparations is sold by Dainippon Printing Co., Ltd. (Kyoto, Japan).
The topical patch preparations that may be terminally sterilized according to the subject methods may be fabricated using any convenient protocol. One convenient protocol for fabrication of such patches includes preparing a gel adhesive paste through the uniform mixing of the aforementioned ingredients and then coating the paste onto support, followed by cutting of the resultant product to the specified size to obtain the desired topical patch preparation. The resultant topical patch preparation is then heat-sealed, typically several sheets to a package, using a packaging material containing an aluminum layer, as described supra, to obtain the sealed topical patch. For a more detailed description of the fabrication protocol, see U.S. Pat. No. 5,827,529; the disclosure of which is herein incorporated by reference.
Terminally Sterilized Topical Patch Preparation
Also provided by the subject invention are terminally sterilized patch preparations, where in many embodiments the patch preparations are terminally sterilized packaged patch preparations, i.e., patch preparations sealed in a package, such as an aluminum foil containing package or envelope, as described supra. Because of the process employed in the subject methods, the subject topical preparations are characterized by the presence of non-viable microorganisms and substantially no viable microorganisms, where in certain embodiments the subject terminally sterilized topical patch preparations include no viable microorganisms. Where the subject terminally sterilized topical patch preparations contain some viable microorganisms, they will not contain so many organisms that they cannot be called terminally sterilized. As such, in these embodiments, the number of microorganisms will not exceed about 100, usually will not exceed about 10 and more usually will not exceed about 1 to 10. Because the subject compositions are prepared from non-sterile components and then terminally sterilized, as opposed to preparations prepared under clean room conditions and protocols, the number of non-viable or irradiation killed microorganisms present in the subject compositions is substantial, and may range from about 1 to 100, usually from about 1 to 50 and more usually from about 1 to 10.
Methods Of Using Patch Preparations
The subject terminally sterilized patch preparations find use in the topical delivery of active agents to a host, where by topical delivery is meant delivery via absorption through the skin. In using the subject terminally sterilized topical patch preparations to topically administer an active agent to the skin, the topical preparation is applied to a skin surface and maintained at the site of application for a period of time sufficient for the desired amount of active agent to be delivered to the host, where the period of time typically ranges from about 1 hr to 24 hr, usually from about 1 hr to 12 hr.
Kits
Also provided are kits, where the subject kits at least include one or more terminally sterilized topical patch preparations, as described above. The subject topical patch preparations in the kits may be present in a package, as described supra. The subject kits also generally include instructions for how to use the patches in active agent delivery to a host. The instructions are generally recorded on a suitable recording medium. For example, the instructions may be printed on a substrate, such as paper or plastic, etc. As such, the instructions may be present in the kits as a package insert, in the labeling of the container of the kit or components thereof (i.e. associated with the packaging or subpackaging) etc. In other embodiments, the instructions are present as an electronic storage data file present on a suitable computer readable storage medium, e.g. CD-ROM, diskette, etc.